Modular unit for multistage flash distillation



y 1970 w. R. WILLIAMSON 3,

MODULAR UNIT FOR MULTISTAGE FLASH DISTILLATION Filed Feb. 13, 1967 4 Sheets-Sheet l I N VENTOR BY M W %)N E Y May 19, 1970 w. R. WILLIAMSON MODULAR UNIT FOR MULTISTAGE FLASH DISTILLATION Filed Feb. 13, 1967 4 Sheets-Sheet 2 INVENTOR M/zZ/z'am Q ifZZ/Zki/ZSUM y 1970 w. R. WILLIAMSON 3,51 7

I MODULAR UNIT FOR MULTISTAGE FLASH DISTILLATION Filed Feb. 13, 1967 4 Sheets-Sheet 5 ago May 19, 1970 w. R. WILLIAMSON MODULAR UNIT FOR MULIISTAGE FLASH DISTILLATION 4 Sheets-Sheet Q Filed Feb. 13,

QNNK ANNNQX RNWQRY QNNK QNNTWWK NQQQ United States Patent 3,513,075 MODULAR UNIT FOR MULTISTAGE FLASH DISTILLATION William R. Williamson, Waterford, Conn., assignor to American Machine & Foundry Company, a corporation of New Jersey Filed Feb. 13, 1967, Ser. No. 615,743 Int. Cl. B01d 3/06; C02b 1/06 US. Cl. 202-173 3 Claims ABSTRACT OF THE DISCLOSURE This disclosure includes drawings and a description of a modular elfect construction for multistage, multiefl'ect distillation plants of the type used to produce fresh water from sea water. The construction comprises an outer shell of low cost structural material and partitioned interiorly to establish upper flash chambers connected to respective lower condenser chambers by vapor ducts formed in part by corrosion resistant interior partitions and in part by the outer shell. The operating pressure loads of the eifect are absorbed by the outer shell.

This invention relates to flash distillation plant constructions, and more particularly, it concerns improvements in the construction of multistage, multieffect, flash distillation plants of the type used in the desalinization of sea water.

In a co-pending application, Ser. No. 615,572 filed concurrently herewith, there is disclosed various forms of modular constructions for flash distillation plants by which self-contained evaporator-condenser modules may be connected in tandem to provide any number of separate stages that may be required for a particular installation. In each of the various structural forms of modules disclosed in that application, the relatively heavy condenser chamber, with its banks of heat exchange tubes, is positioned below and provides support for an upper structure defining the flash chamber. Various forms of the modular constructions disclosed in that co-pending application also isolate contact of corrosive feed solutions with wall components that do not supply strength required to resist pressure differentials employed in operation. Hence, it is apparent that the modular construction disclosed in the aforementioned co-pending application results in reduced costs both from the standpoint of materials needed to support the various physical loads incurred and also from the standpoint of minimizing the amount of high cost, corrosion resisting alloys needed to handle the corrosive brine.

The present invention is related to the invention disclosed in the aforementioned co-pending application and involves an improved modular unit that is particularly suited for use in multistage, multieffect flash evaporation plants. In accordance with the present invention, each eflect for a multieffect plant is established by the signal outer shell formed of low cost structural material subject to corrosion by the brine, such as carbon steel in plate form, and the interior of the shell separated into multiple pressure-temperature stages by prefabricated partition units formed of light gage corrosion resisting materials, such as copper-nickel alloys, to establish a flash chamber, a condenser chamber, and a vapor duct interconnecting the flash chamber and condenser chamber of each respective stage. The stages Within each effect, are arranged transversely of the outer shell and connected successively in series fashion so that brine flow between the flash chambers of each stage is in a generally sinusoidal path. Condensing fluid flow through the condenser chamber of each stage is similarly arranged to facilitate "Ice the passage of relatively cool condenser fluid sinusoidally in counter flow relationship with the flow of brine through the flash chambers. The length of each flash chamber is also less than the transverse dimension of the outer shell and the flash chambers are in staggered relation so that one end of each flash chamber adjacent the inlet nozzle of the flash chamber forms with the outer shell, a vapor duct interconnecting the upper portion of the flash chamber to its respective condenser chamber.

A principal object of the present invention is the provision of an improved modular unit to establish one effect of a multistage, multieflect flash evaporation plant in which the loading stresses imposed by negative operating pressure in the effect may be absorbed by low cost structural material, leaving only those portions which are contacted by corrosive feed solutions to be formed of relatively high cost corrosion resisting materials.

Another object of this invention is to provide a multistage, multieifect flash evaporation plant modular design Which is adaptable to various sizes of plants and yet makes maximum use of prefabricated stock partition elements, thereby reducing the inventory of different parts required for production of such plants.

A further object of this invention is to provide a multistage, multietfect flash evaporation plant module which is adapted to various conditions of operation and which reduces to a minimum, the space requirements needed for a given capacity installation.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description to follow taken in conjunction with the accompanying drawings in which:

FIG. 1 is a top plan view of a module forming a multistage, flash distillation effect in accordance with the present invention with the top wall or cover thereof removed;

FIG. 2 is a vertical cross-section taken on line 2-2 of FIG. 1;

FIG. 3 is a vertical cross-section taken on line 3-3 of FIG. 1; and

FIG. 4 is a schematic view illustrating one way in which the modular units of this invention may be used in practice.

As shown in FIGS. 1-3 of the drawings, the multistage effect module of the present invention includes an outer shell, generally designated by the reference numera1 10, and formed by top, bottom, side, and end Walls 12, 14, 16 and 18, respectively. Each of these walls is formed preferably of pre-cut carbon steel plates /2" in thickness and their assembly into the generally rectangular shell secured by suitable means such as welding.

As shown most clearly in FIGS. 2 and 3 of the drawings, the shell 10 is divided interiorly by a series of horizontal partitions or plates 20 to establish an upper flash space further divided into four flash chambers 22a-d and a lower condenser space divided by vertical plates 24 into four condenser chambers 26ad. As will be noted in FIG. 1 of the drawings, each of the four plates or horizontal partition members 20 is identical in size and shape and further, that each is bounded by vertical partition means to establish the flash chambers 22a-d which partition means will be described in more detail below. The length of each of the plates 20 is less than the transverse dimension between the side walls 18 of the outer shell 10 to accommodate vertical vapor ducts 28a-d. The vapor ducts establish fluid communication between the respective flash chambers 22a-d and the condenser chambers 26a-d.

As shown in FIG. 1 of the drawings, the vertical partitions establishing the respective flash chambers 22a-d include a series of wall plate members 30 secured by welding between the floor plate 20 and a series of transverse steel bars 31 underlying the top wall 12 of the exterior shell. The remaining vertical walls of the end flash chambers 22a and 22d are established by a generally U-shaped wall member 32 welded to the adjacent wall 30 and cut out at the leg thereof adjacent the ducts 28a. and 28d so as to permit the passage of vapors thereover and into these ducts respectively. This communication path is shown most clearly in FIG. 2 of the drawings. Also, it will be noted that a demisting screen 34 extends over the complete top of each flash chamber as defined by the upper edge of the aforementioned end wall of the flash chamber adjacent its respective vapor duct.

The end walls for the flash chambers 22b and 220 are formed by reversely bent wall members 36 which also are welded to the transversely extending plates 30. Each of the partition members 30, 32 and 36 as well as the four plates 20 are formed of corrosion resistant, copper-nickel alloy plate stock. Specifically, the four plates 20 in the embodiment shown are formed of plates whereas the vertical partition wall members 30, 32 and 36 are formed of copper-nickel plate stock of between A3 and inches in thickness.

Each of the flash chambers 22a-d includes an evaginated venturi nozzle for the introduction of brine or feed solution. As shown in FIG. 2, the nozzle in each flash chamber is located adjacent its respective vapor duct 28 and includes an inclined weir plate 38 and an inclined top plate 40. Brine feed solution is introduced through the nozzle to the first flash chamber stage 22a through a flanged inlet nipple 42 and is passed to the next stage through an aperture 44 on the opposite end thereof from the nozzle and formed in the vertical Wall plates 30. It will be appreciated the aperture 44 provides the inlet aperture for the next succeeding flash chamber 22b. Also, the residual liquid brine passes through similar apertures 44 in the plates 30 separating the flash chambers 22c and 22d. Residual brine from the chamber 22d is passed through a flanged outlet nipple 45.

It will be noted that those portions of the vertical partition walls 32 and 36 which are positioned next to the side and end walls of the outer shell are spaced slightly from the outer shell and are in communication with an adjacent vapor duct 28. In this manner, the negative loading of each flash chamber stage in the multistage effect is imposed on the outer shell walls and not on the relatively thin corrosive resistant plate members forming the walls 32 and 36. Hence, the only differential pressure loads to which the internal partitions are subjected are those existing between stages or across the wall plates 30, a relatively small pressure differential which is readily handled by light gage plate stock of the type aforementioned. Also it will be noted that sight glasses 46a-d are mounted on the shell to render each flash chamber visible from the exterior of the shell.

Positioned within each of the condenser chambers 26a-d are a series of straight heat exchange tubes 48 opening through tube sheets 50 secured to a steel flange 52, in turn welded to the opposed side walls 16 of the outer shell 10. To assure intimate contact between vapors, passed through the ducts 28a-d, and the tubes 48 in each condensing chamber, three vertical baffle plates 54 are provided, each extending from the floor plates or the bottom wall 14 of the shell. These baflle plates also serve as intermediate supports for tubes 48. As shown in FIG. 2 of the drawings, the baffle plates are spaced at successively smaller increments toward the end of the condenser chambers opposite the respective vapor duct 28.

To enable condensing fluid to pass between the tubes 48 in the respective condenser chamber 26a-d, semi-cylindrical headers 58 and 60 are bolted or otherwise secured over the tube sheets 50 along each side of the shell 10. While the exterior shape of the headers 58 and 60 is substantially the same, the interior of the header 60 is divided by a central vertical partition plate 62 to direct the flow of condensing fluid between the chambers 22a and 22b, and

22c and 22d in series fashion. The header 58, is provided with a pair of similar partition plates 64 to direct the condenser fluid flow into the end condenser chamber 26a, between the condenser chambers 26b and 26c and out of the condenser chamber 26d. For each condenser chamber 26, the header 58 is provided with downwardly directed flanged nipples 66a-d for connection to external lines as required by the mode of plant operation desired. One such operation mode is described generally below.

A distillate trough 68 extends along the underside of the bottom plate 14 and is in communication with each of the condenser chambers 2611-11 through ports 70 formed therein. Similarly, the condenser chambers are ported through vents 72 to establish the operating negative pressure differential between each of the successive stages housed within the shell 10. The connection of these vents 72 to a source of negative pressure is conventional and well known by those skilled in the art.

To provide a clear understanding of the manner in which the modular effect construction of this invention might be used in practice, reference is made to FIG. 4 of the drawings which shows a three effect plant employing the modules described above and designated by the reference numerals 10, 10 and 10 respectively. Though the schematic illustration in FIG. 4 is simplified and also is but one possible way in which the modules of this invention might be used, it will be noted that raw sea water is fed first through the lower pressure stages 26d and 260 of the lowest pressure effect 10. A portion of the sea water passing from the condenser tubes into the chamber 260 is treated and reintroduced into the condenser chambers 26a and 26b of the higher two stages in the low pressure effect 10 In order to supply heat for brine in the flash chambers 22a d of the third effect 10 the treated feed is passed through the condenser chambers 26d and 26c of the lower pressure stages of the second or intermediate pressure effect 10 A portion of this feed is mixed with the brine blow-down from the second effect and introduced into the flash chambers 2241 -11 of the third effect 10. A portion of the feed passing from the condenser chambers 220 is mixed with re-cycle brine in the second effect by appropriate pipes connected between the downwardly facing flange nipples 66b and 660 (see FIGS. 1 and 2). Similarly, heat for the second effect is developed by passing feed through the condenser chambers 22c and 26d in the lower pressure stages of the first effect, whereas heat for the first effect is supplied by the heater shown.

Thus it will be appreciated that by this invention there is provided an extremely effective modular unit particularly suited for use in a multistage, multieffect flash distillation plant. The complete pressure loading of each effect which, as shown in FIG. 4 of the drawings, may be as much as 25 pounds per square inch, is carried by the outer shell 10 whereas the relatively light pressure differentials between each stage within an effect are absorbed by the relatively high cost corrosion resisting interior partition plates. Also it will be noted that since the flash chambers 22a-d are positioned above the condenser chambers 26a-d in each effect, the problems associated with maintaining a pressure head at the intake of the re-cycle brine pumps are minimized. These problems are caused by the volatile nature of the brine at the pressures involved and are minimized simply by virtue of the elevation at which the flash chambers are maintained relative to the condenser chamber and the remaining structure of each unit. Hence, with the present invention, it is unnecessary to locate the re-cycle brine pumps any significant distance below the bottom of each unit. Also, the organization of the vapor ducts together with the design of the flash chamber nozzles including the upper plate 40 to constrain the corrosive brine to the lower portion of each flash chamber enables the use of substantially open-top flash chambers from the standpoint at least of high cost, corrosion resistant wall members for the flash chamber.

Since variations in the construction shown and illustrated herein are possible, it is expressly intended that the foregoing description is illustrative of a preferred embodiment only, not limiting, and that the true spirit and scope of the present invention is to be determined by reference of the appended claims.

I claim:

1. A modular unit to form a multistage effect in a flash distillation plant of the type in which a liquid solution is separated into a vapor fraction and a residual liquid fraction, the vapor fraction condensed and discharged as a liquid distillate, and in which relatively cool liquid solution is circulated as condensing fluid in counter-flow relation to heated solution passed through successive stages and effects, including means for brine blowdown and recycling, said modular unit comprising an outer shell having top, bottom, side and end walls, said walls being formed from low cost structural material subject to corrosion by said solution, horizontal partition means connected to a U-shaped wall member and defining a flash space within said outer shell, said horizontal partition means comprising a series of partitions dividing the interior of said shell into an upper flash space and a lower condenser space, vertical partition means in said upper space defining side end walls, the flash space being divided into a plurality of adjacent flash chambers, the side walls of a flash chamber extending transversely of said shell and being shorter than the distance between the said walls of said shell to provide a vapor duct between one end wall of each flash chamber and a side wall of said shell, the upper edge of said one end wall being spaced from the top wall of said shell to place said flash chambers in fluid communication with said vapor ducts, respectively, said horizontal and vertical partition means of said flash space being formed of relatively high cost, corrosion resistant material; a plurality of transverse partition walls dividing said lower space into a plurality of condenser chambers, one of such condenser chambers for each of said adjacent flash chambers, said condenser chambers being in fluid communication with said flash chambers respectively, through said vapor ducts; heat exchange elements in each of said condenser chambers extending transversely and including a pair of headers one of said headers being provided with a coupling pipe member for each of said condenser chambers.

2. The apparatus recited in claim 1 in which said flash chambers are in staggered relation so that the vapor ducts communicating with successive flash chambers are located respectively on opposite sides of said shell.

3. The apparatus recited in claim 2 in which the vertical partition walls forming the ends and sides of said flash chambers adjacent said outer shell are spaced from the respective sides and end walls of said outer shell, the space thus defined being in communication with an adjacent one of said vapor ducts.

References Cited UNITED STATES PATENTS 2,078,377 4/1937 Fox et a1 202-74 2,171,549 9/1939 Gordon et al. 20386 X. 2,398,068 4/ 1946 Worthen et al. 202-174 3,119,752 1/1964 Checkovich 202173 X 3,261,766 7/1966 Sherwood 202174 X 3,320,137 5/1967 Jebens et al. 20 2-173 3,322,648 5/1967 Kays et al. a- 202l74 3,142,381 7/1964 Ris et al. 203-11 X 3,285,832 11/1966 Sephton 202-173 FOREIGN PATENTS 13,545 5/1928 Australia.

NORMAN YUDKOFF, Primary Examiner F. E. DRUMMOND, Assistant Examiner US. Cl. X.R. 203---88, 11 

